The invention relates to waterborne ultraviolet curing gloss oil and a preparation method thereof. The preparation method of the waterborne ultraviolet curing gloss oil comprises the following steps: mixing diisocyanate with dihydric alcohol, and reacting, so as to obtain a first reaction liquid; adding dihydroxy carboxylic acid and a catalyst into the first reaction liquid, reacting to obtain a second reaction liquid, mixing the second reaction liquid with a chain extender, and reacting to obtain a third reaction liquid; adding an alkene end-capping agent and a polymerization inhibitor into the third reaction liquid, reacting to obtain a fourth reaction liquid, adding triethylamine into the fourth reaction liquid, and reacting to obtain a polyurethane acrylate prepolymer; and adding deionized water into the polyurethane acrylate prepolymer, emulsifying and dispersing to obtain polyurethane acrylate dispersion, mixing the polyurethane acrylate dispersion, a photoinitiator, a defoaming agent and a levelling agent, stirring and dispersing for 15-30 minutes, so that the waterborne ultraviolet curing gloss oil is obtained. The waterborne ultraviolet curing gloss oil prepared by adopting the method has relatively high performance.